Sutures



United States Patent SUTURES Edward L. Howes, New York, N. Y.

No Drawing. Application June 25, 1953,

Serial No. 364,205

6 Claims. (Cl. 128-3355) This application relates to sutures to be usedin surgery which can be boiled or sterilized by heat in the usualautoclave and yet are self-sterilizing to the degree that they willresist bacterial contamination when placed in the wound and will tend todestroy bacteria in their location in the tissues, thereby reducing thepossibility of infection in the wound. My sutures have high tensilestrength, good workability and are more readily encapsulated in thetissues than the sutures usually employed. They also show very littledanger of secondary extrusion.

The sutures of this invention comprise a fibrous base preferably oftwisted silk or cotton impregnated with a dilute solution of an organicfiller material such as a proper plastic or high melting point wax whichwhen dried and hardened will withstand boiling, together with a verysmall percentage of anti-bacterial agent which preferably has sometendency to combine with the proteid of the silk.

Thus far I have found only one type of plastic which is soluble in avolatile solvent which is available for my purpose, and which willwithstand the sterilizing treatment. This is a combination of vinylidinechloride and vinyl chloride sold under the trade name of Saran B. Theuse of a soluble impregnating material is important because by forming adilute solution the plastic material can be carried into the very fibersof the support medium and distributed through the support medium withoutfilling the interstices between the separate strands which would tend togive the support medium a somewhat slick surface. It is important thatthe suture retain the normal appearance and structure of the fibrousthread so that granulations may grow into it whereby the suture willbecome fixed in the tissue. While I prefer to use a soluble plastic, asstated, I can also obtain valuable results by using soluble waxes havinga melting point substantially above 100 C. Most of these waxes aresynthetic and are sold under trade names such as Acrowax C, Alcowax andStantowax P. A natural wax that can be employed is cranberry wax.

Bactericidal substances which may be employed include the phenylmercuric salts such as phenyl mercuric chloride, phenyl mercuricbenzoate, phenyl mercuric acetate and phenyl mercuric borate. Otherbactericidal agents which may be used and which fall in the groupdefined above include the salts of sulfamylon such as the hydrochlorideand the mandelate salts.

The solvent selected should be volatile and preferably should be asolvent for both the plastic or waxy material and the anti-bacterialagent. My preferred solvents are tetrahydrofuran or 1-4 dioxane. Othersolvents that may be employed include cyclohexanone and cyclopentanonebut if these are used with waxes they should be employed hot, as waxestend to settle out at room temperature.

In forming the suture, a dilute solution of the Saran in the solvent isprepared which may contain, for example, between 2% and 5% by weight ofsolids. With this is included from about .01% to .025 (preferably about.02%) of the bactericidal agent. The fibrous support, which as stated ispreferably twisted thread of silk or cotton of a type appropriate foruse in sutures, is then drawn through the solution. Excess liquid isallowed to drain off and the solvent is then dried out. Withtetrahydrofuran the evaporation takes place almost immediately, whereaswith dioxane it may be desirable to dry the suture with some slightheating before it is wound on a reel, say at a temperature of about C.

I have found that a suture such as described has great benefits. First,on the purely mechanical side, the impregnation permits me to use atwisted thread rather than a braided one without danger of-the endsfraying. A twisted thread in and of itself is stronger than a braidedthread and the impregnation appears to add to the strength so that theimpregnated twisted thread of my invention is approximately 20% strongerthan a coresponding unimpregnated braided thread. The impregnation alsogives some stiffness to the suture making it easier to use in theoperating room. The use of a twisted thread rather than a braided one isalso valuable because with the twisted thread encapsulation has beenfound to take place about fifteen days earlier than with the braidedthread. In ordinary case twisted threads fray out too readily to begenerally useful but this is largely prevented by the impregnatron.

While the mechanical improvements of my suture are valuable, the mostimportant feature is found in the antibacterial qualities. The plasticor waxy material tends to hold the bactericidal agent in place so thatit is not readily removed during sterilization and this is furtherassisted by the aifinity between the bactericidal agent and the proteidin the silk. At the same time the solid impregnating material issufficently porous (perhaps due to the fact that a low concentrationsolution was employed and the solvent subsequently evaporated off) so asufficient amount of the bactericidal agent gradually finds its way tothe surrounding tissues, with the result that bacteria in theneighborhood of the suture are destroyed and the possibility ofinfection in the wound is much reduced. I have found, for example, thatthe mercuric salts are particularly useful as they are destructiveagainst both gram positive and gram negative bacteria. At the same timetheir solubility is relatively low and they do not provoke unnecessarytissue reactions and are not toxic, allergenic or carcinogenic.Encapsulation takes place rapidly and the threads become firmly fixed inthe tissues. There is no more inflammatory reaction than with theunimpregnated sterilized thread and there is a marked reduction in thebacteria surrounding the thread so that post-operative extrusion orsloughing is greatly minimized.

In making my suture I prefer to use the binder and bactericidalmaterials in one single bath as has been described but valuable resultscan be obtained if two separate baths are used, in which case eachsolvent may be employed for the two impregnating materials. In such casethe thread is preferably impregnated with the dilute solution ofbactericidal agent and then with the binder material. It is understoodthat in any case the amount of impregnating material employed will beinsufiicient to coat the thread as a whole by entirely filling thedepressions between the strands, or to substantially increase itsdiameter.

What I claim is:

1. A surgical suture consisting of a thread of natural fiber whichretains the appearance and structure of the thread but which isimpregnated with a small percentage of an anti-bacterial agent and amaterial of a plastic nature that is soluble in an organic solvent sothat it may be applied in a dissolved state and which is substantiallyunaffected by being boiled in water, such material being selected fromthe group consisting of the plastic formed by the combination ofvinylidine chloride and vinyl chloride, and the high melting point waxesand such material being used in an amount insufiicient to fill theinterstices betweenthe strands of the thread to render the surface ofthe thread slick and impermeable.

2. A suture as specified in claim 1 in which the antibacterial agent isa phenyl mercuric salt.

3. A suture as specified in claim 1 in which the thread is twisted silk.

4. A surgical suture consisting of a twisted thread of silk impregnatedbut not coated with a small percentage of phenyl mercuric salt and theplastic formed by the combination of vinylidine chloride and vinylchloride.

5. The method of preparing a suture which comprises forming a dilutesolution in an organic solvent of an antibacterial agent and a materialof a plastic nature which is substantially unafiected by being boiled inwater, such material being selected from the group consisting of theplastic formed by the combination of vinylidine chloride and vinylchloride and the high melting point waxes, impregnating a thread ofnatural fiber With such solution in an amount such that the solution isinsufiicient to fill the interstices between the fibers and therebyrender the surface of the thread slick and impermeable to water anddrying.

6. A method as specified in claim 5 in which the antibacterial agent isa phenyl mercuric salt and the plastic material employed is the plasticformed by the combination of vinylidine chloride and vinyl chloride andin which the solution contains between about 2% and 5% of solidsincluding between about .01% and .025 of the phenyl mercuric salt.

References Cited in the file of this patent UNITED STATES PATENTS1,202,931 Watson Oct. 31, 1916 1,741,893 Watson Dec. 31, 1929 1,942,061Hofmann Jan. 2, 1934 2,099,688 Hill Nov. 23, 1937 2,567,905 Field Sept.11, 1951

1. A SURGICAL SUTURE CONSISTING OF A THREAD OF NATURAL FIBER WHICHRETAINS THE APPEARANCE AND STRUCTURE OF THE THREAD BUT WHICH ISIMPREGNATED WITH A SMALL PERCENTAGE OF AN ANTI-BACTERIAL AGENT AND AMATERIAL OF A PLASTIC NATURE THAT IS SOLUBLE IN AN ORGANIC SOLVENT SOTHAT IT MAY BE APPLIED IN A DISSOLVED STATE AND WHICH IS SUBSTANTIALLYUNAFFECTED BY BEING BOILED IN WATER, SUCH MATERIAL BEING SELECTED FROMTHE GROUP CONSISTING OF THE PLASTIC FORMED BY THE COMBINATION OFVINYLIDINE CHLORIDE AND VINYL CHLORIDE, AND THE HIGH MELTING POINT WAXESAND SUCH MATERIAL BEING USED IN AN AMOUNT INSUFFICIENT TO FILL THEINTERSTICES BETWEEN THE STRANDS OF THE THREAD TO RENDER THE SURFACE OFTHE THREAD SLICK AND IMPERMEABLE.